#include <stdio.h>

int main()
{
    int a[9] = {9,8,7,6,5,4,3,2,1};
    int b[9] = {1,2,3,4,5,6,7,8,9};
    int c[20] = {0};
    int start = 0;
    int count = 0;
    for(int i = 0;i < 9;i++)
    {
        for(int j = 0;j < 9;j++)
        {
            c[i+j] += a[i] * b[j];
        } 
    }
    for(int i = 0;i < 20;i++)
    {
        c[i] += count; 
        count = 0;
        if(c[i] >= 10)
        {
            count = c[i]/10;
            c[i] -= count * 10;
        }
    }
    int flag = 0;
    for(int i = 19;i >= 0;i--)
    {   
        if(c[i] != 0)
        {
            flag = 1;
        }
        if(flag)
            printf("%d",c[i]);//121932631112635269
    }
    printf("\n");
    return 0;
}